It would have been easy for Eric Ste Marie to mistake the bobbing brown head and body in the Detroit River to be a muskrat, but curiosity drove him to chase it as it swam towards Ambassador Bridge in Southeast Michigan.

It turns out, it was the first "straight-up river otter" to be seen in the Detroit River in over 100 years. Ste Marie double-checked with a biologist friend of his from the University of Windsor, who confirmed—after watching the grainy cell phone video—that it really was a North American river otter.

The reaction from some local experts he spoke to was of disbelief, given that it's been over a century sine one has last been seen here. The feeling was also of hope, as otters are a keystone species that signify good water health.

The otters and beavers of North America fueled the fur trapping industry for decades, and after the last one was extirpated from Detroit, river pollution kept them coming back—until now.

Fox 2 reports that otters were released in eastern Ohio some years ago, and over time they made their way into Michigan.

"So the otters are kind of like, the flagship or the symbol of the healing ecosystem and at the end of the day that benefits everyone in the area," Ste Marie told Fox.

(WATCH the Fox 2 video for this story below.)

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